Re: Wrong approach
It worked in 1970. At college all of the students got offers from the Colombia Record Company and many of the students were stuffing all of the prepaid envelopes with their advertising material and returning it. We, in the computer department, had many boxes of full 5081 punched card boxes to which we taped the return envelop and mailed them. Running out of cards we filled one box with sand. (A mailbox only took 8 boxes before the door wouldn't open.)
The next day the business manager of the computer center gets a call from the post office (since some of the boxes had computer department labels on them) asking if he wanted to send someone to the post office to seal the box that was leaking sand so that all of the precious sand would make it to the recipient. He didn't know anything about this so the postmaster said he was going to call Colombia Records so they could send someone to seal the box. He said that it was going to cost about $500 to send all of these boxes. Colombia records replied with a stop order for anything over 5 pounds so they never got the cards and sand.
The students stopped getting Colombia Record Club solicitations shortly afterwards though.